Calculation of the distortion coefficient and associated uncertainty of PTB and LNE 1 GPa pressure balances using finite element analysis—EUROMET project 463

Abstract

Results for pressure distortion coefficients (λ) obtained by five national metrology institutes with finite element methods (FEM) for PTB and LNE 1 GPa piston-cylinder units are presented. For the PTB unit they demonstrate good agreement of the FEM and the experimental distortion coefficients but rather large differences in the uncertainties, pressure distributions, gap profiles and piston fall rates. The reasons for differences between the theoretical real-gap and experimental λ obtained for the LNE unit require further clarification. The uncertainty of the gap geometry is identified as the main uncertainty source.

Elastic Distortion Calculation of a Controlled-Clearance Piston-Cylinder Assembly up to 1500 MPa Using Finite Element Method

“…These results, working as load, are responsible for the corresponding rapid decent of gap clearance shown in figure 6. Compared to other models in the literature [12][13][14], this PCA has a relatively large nominal gap clearance and a "soft"…”

“…Such controlled-clearance (CC) type of piston gauge was first proposed by Johnson and Newhall [1] and has been widely accepted and used by national metrology institutes [2][3][4]. It has been intensively studied in the past using various techniques [4][5][6][7][8][9][10][11][12][13][14][15]. Among these studies, finite element method (FEM) has been proven available and efficient to determine the distortion of piston and cylinder, especially in the piston-cylinder engagement gap [11][12][13][14][15].…”

“…It has been intensively studied in the past using various techniques [4][5][6][7][8][9][10][11][12][13][14][15]. Among these studies, finite element method (FEM) has been proven available and efficient to determine the distortion of piston and cylinder, especially in the piston-cylinder engagement gap [11][12][13][14][15]. This study develops a numerical model using FEM and fluid mechanics to calculate the elastic distortion of a CC piston-cylinder assembly (PCA).…”

Pistonlu Basınç Standartlarında Piston ve Silindir Arasındaki Boşlukta Oluşan Basınç Dağılımının Hesaplanması

“…Diğer taraftan pistonlu basınç standardına ait basınç distorsiyon katsayısı ise tek basına Dadson Theory ile belirlenemez. Basınç distorsiyon katsayısının belirlenebilmesi için sonlu elemanlar yöntemine dayalı bir metot kullanılabilmektedir [2][3][4]. Buradaki ilk aşama farklı basınç noktalarında piston silindir arasındaki basınç dağılımının hesaplanmasıdır.…”

FEA calculation of pressure distortion coefficients of gas-operated pressure balances – EURAMET project 1039

“…However, when a very low uncertainty of a gas pressure is necessary as, e.g., in experiments on the determination of the Boltzmann constant by dielectric constant gas thermometry (DCGT), in which the relative standard uncertainty of absolute pressure up to 7 MPa in helium of only 1 Â 10 À6 is needed, a sufficiently low uncertainty of k of gas pressure balances is required [1]. Finite Element (FE) Analysis (FEA)-based methods for liquid-operated pressure balances have been established and applied within EURAMET project 463 [2]. The actual EURAMET project numbered 1039 was aimed at the development and application of FEA methods to calculate k of gas pressure balances.…”